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Biomedical subjects

J Chow

Publications and source records attributed to J Chow.

At least 73 records · Page 4Linked to original sources
PubMed1991

High concentrations of 17 beta-estradiol stimulate trabecular bone formation in adult female rats.

Although the effects of low concentrations of 17 beta-estradiol (E2) on bone formation and resorption are well described, little is known of the effects of E2 on bone at concentrations that circulate during pregnancy. We, therefore, investigated the effects of administration of high dose E2 to 3-month-old female Wistar rats on biochemical and histomorphometric indices of bone formation and resorption. Animals receiving exogenous E2 (4 mg/kg.day for 17 days; n = 9) showed a mean serum E2 concentration of 17.5 +/- 2.9 nM, compared with 0.6 +/- 0.2 nM in those receiving vehicle alone (n = 10). The bone formation rate, measured at the proximal tibial metaphysis after the administration of double fluorochrome labels, was greatly increased in the E2 group (13.6 +/- 2.0 x 10(-2) microns3/microns2.day) compared to controls (3.9 +/- 0.9), as was serum alkaline phosphatase (E2, 133.6 +/- 10.1 IU; controls, 87.5 +/- 5.5). This increase in the rate of bone formation was associated with a significant increase in trabecular bone volume. E2 treatment did not affect urinary hydroxyproline excretion or histomorphometric indices of bone resorption. These findings suggest that high concentrations of E2 strongly stimulate the formation of trabecular bone. This may represent an important mechanism by which calcium stores are accumulated during pregnancy in rats, in anticipation of the mineral requirements of lactation.

Alkaline Phosphatase↗
PubMed1990

Synthetic HIV-2 protease cleaves the GAG precursor of HIV-1 with the same specificity as HIV-1 protease.

A 99-amino acid protein having the deduced sequence of the protease from human immunodeficiency virus type 2 (HIV-2) was synthesized by the solid phase method and tested for specificity. The folded peptide catalyzes specific processing of a recombinant 43-kDa GAG precursor protein (F-16) of HIV-1. Although the protease of HIV-2 shares only 48% amino acid identity with that of HIV-1, the HIV-2 enzyme exhibits the same specificity toward the HIV-1 GAG precursor. Fragments of 34, 32, 24, 10, and 9 kDa were generated from F-16 GAG incubated with the protease. N-terminal amino acid sequence analysis of proteolytic fragments indicate that cleavage sites recognized by HIV-2 protease are identical to those of HIV-1 protease. The verified cleavage sites in F-16 GAG appear to be processed independently, as indicated by the formation of the intermediate fragments P32 and P34 in nearly equal ratios. The site nearest the amino terminus is quite conserved between the two viral GAG proteins (...VSQNY-PIVQN...in HIV-1,...KGGNY-PVQHV...in HIV-2). In contrast, the putative second site (...IPFAA-AQQKG...) of HIV-2 GAG shares minimal sequence identity with site 2 of HIV-1 GAG (...SATIM-MQRGN...). These sequence variations in the substrates suggest higher order structural features that may influence recognition by the proteases. Pepstatin A inhibits HIV-2 protease, whereas 1,10-phenanthroline and phenylmethylsulfonylfluoride do not; these results are in agreement with the finding that proteases of HIV and other retroviruses are aspartyl proteases.

Amino Acid Sequence↗
PubMed1990

Human beta nerve growth factor obtained from a baculovirus expression system has potent in vitro and in vivo neurotrophic activity.

A baculovirus expression vector, which contains the coding sequences for human prepro (beta) nerve growth factor under control of the viral polyhedrin promoter, was constructed. Upon infection of insect cells with the recombinant virus, mature human beta nerve growth factor (rhNGF) was released into the culture fluid. The mature rhNGF was biologically active since rat pheochromocytoma (PC12) and human neuroblastoma (SH-SY5Y) cells were induced to extend neurites upon treatment with this material. This activity was abolished by treating with antiserum prepared against mature mouse beta NGF (mNGF). When compared with mNGF, rhNGF more rapidly elicited the differentiation response in both PC12 and SH-SY5Y cells. In an in vivo assay of cholinergic cell survival, rhNGF was nearly as potent as mNGF in protecting cholinergic neurons from degeneration following a fimbria-fornix lesion. These results show that the baculovirus expression system provides quantities of biologically potent human beta NGF suitable for a comprehensive program of research to ascertain beta NGF's potential as a therapeutic agent for the treatment of Alzheimer's disease.

Animals↗
PubMed1990

Ethnicity, self-care, and use of medical care among the elderly with joint symptoms.

Elderly individuals with self-reported joint symptoms representing three ethnic groups (i.e., blacks [n = 105], Hispanics [n = 100], and whites of Eastern European origin [n = 112] answered questions about their use of self-care and medical care for these symptoms. Ethnic groups differed in both self-care practices and their use of medical care for joint symptoms. Multiple regression analyses demonstrated that arthritis-specific and general health status were better predictors than ethnicity of the tendency to rely on self-care and medical care. There was no evidence that self-care served as a substitute for medical care.

Aged↗
PubMed1989

Locus of control and decision making for posthospital care.

Discharge planning involves making choices about the type and amount of posthospital care a patient will receive within the reality of resource constraints. Elderly patients discharged from an acute-care hospital vary in their reactions to this decision-making process and the degree to which they exert final control over the decision. Perceived lack of control over the decision is associated with posthospital psychological distress for patients with high levels of internal locus of control, but not for those whose expectations for internal control are low.

Adaptation, Psychological↗
PubMed1988

Dual genotype in cutaneous T cell lymphoma: immunoglobulin gene rearrangement in clonal T cell malignancy.

Genomic DNA digests of peripheral blood lymphocytes from 13 patients with the leukemic phase of the T cell neoplasm cutaneous T cell lymphoma were studied by hydridization using probes for the constant region of the beta chain of the T cell receptor, the joining region of the immunoglobulin heavy chain gene, and the kappa and lambda light chain genes. Lymphocytes from all 13 cutaneous T cell lymphoma patients contained DNA with clonal rearrangements of the beta chain gene of the T cell receptor. In addition, DNA from 4 patients contained an immunoglobulin gene rearrangement. T cell enrichment studies of peripheral blood lymphocytes from 2 patients confirmed that the immunoglobulin gene joining region rearrangement was confined to the T cell population. These results demonstrate that cutaneous T cell lymphoma is a clonal T cell malignancy that frequently expresses a dual genotype. A multiparameter approach, including DNA probes for the beta chain of the T cell receptor, as well as the immunoglobulin genes, immunophenotyping, and cytogenetics, is valuable in the diagnosis of cutaneous T cell lymphoma.

Antibodies, Monoclonal↗
PubMed1988

The effects of combining felodipine and metoprolol in moderate to severe hypertension--a one year study.

A dose titration study was performed using felodipine, a new calcium antagonist, in Chinese patients with essential hypertension inadequately controlled by metoprolol alone (DBP greater than 95 mmHg). BP and pulse rate were recorded at rest and during treadmill exercise. Nineteen patients completed the six weeks' dose titration phase (2.5-5-10 mg twice daily) of whom 17 were followed for one year. A single 2.5 mg dose of felodipine produced a rapid and pronounced antihypertensive response with pre-exercise supine BP falling from a mean 168/104 to 146/92 mmHg) (P less than 0.001). The SBP during exercise was reduced from 206 to 185 mmHg (P less than 0.001). After 6 weeks treatment the supine BP had fallen to 132/85 mmHg (P less than 0.001) and the SBP during exercise to 169 mmHg (P less than 0.001). Six patients received 2.5 mg twice daily, eight patients 5 mg twice daily and three patients 10 mg twice daily. The effects, both at rest and during exercise, were maintained for at least 12 hours after dosing. The pulse rate was unaffected by felodipine therapy apart from a small transient increase following the first dose. Sixteen patients achieved the target DBP of 90 mmHg measured 12 hours after dosing and only one patient still had a DBP greater than 95 mmHg. After one year the mean supine BP had fallen slightly further to 128/82 mmHg. One patient was withdrawn due to palpitations. Felodipine was otherwise well tolerated.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1988

Revalidation and expansion of an adolescent substance abuse screening measure.

The perceived-benefit-of-drinking scale has been developed to assess reasons for drinking in an adolescent population. In this study, the self-administered questionnaire, which has been expanded to include a reason-for-drug-use scale, was completed by 1363 junior and senior high school students. A comprehensive battery of analytic techniques was used to investigate the performance of these perceived-benefit scales on this larger and wider age-range sample. The results confirmed the reliability and validity of the instrument. The findings showed the two scales to perform well across a range of sociodemographic and age groups. These data reassert the strength of the approach and support the instrument's potential as a tool for clinically assessing adolescent substance use.

Adolescent↗
PubMed1987

HTLV-I-associated lymphoma involving the entire alimentary tract and presenting with an acquired immune deficiency.

A patient with HTLV-I-associated adult T cell lymphoma presented like a patient with the acquired immune deficiency syndrome (AIDS) with peripheral lymphadenopathy, profuse diarrhea, weight loss, night sweats, and multiple opportunistic infections. Infections included cytomegalovirus, Pneumocystis, Histoplasma, Strongyloides, Giardia, and Staphylococcus aureus. Histoplasma has not previously been associated with this lymphoma. The lymphoma involved the entire alimentary tract from pharynx to rectum, which has not previously been reported for adult T cell lymphoma, and is rare for any lymphoma, with only one case reported in this century. Despite extensive gastrointestinal involvement, steatorrhea was not present, perhaps due to preservation of normal intestinal villous architecture.

Acquired Immunodeficiency Syndrome↗
PubMed1987

Comparison of automated pre-column and post-column analysis of amino acid oligomers.

It has been shown that various amino acids will polymerize under plausible prebiotic conditions on mineral surfaces, such as clays and soluble salts, to form varying amounts of oligomers (n = 2-6). The investigations of these surface reactions required a quantitative method for the separation and detection of these amino acid oligomers at the picomole level in the presence of nanomole levels of the parent amino acid. In initial high-performance liquid chromatography (HPLC) studies using a classical postcolumn o-phthalaldehyde (OPA) derivatization ion-exchange HPLC procedure with fluorescence detection, problems encountered included lengthy analysis time, inadequate separation and large relative differences in sensitivity for the separated species, expressed as a variable fluorescent yield, which contributed to poor quantitation. We have compared a simple, automated, pre-column OPA derivatization and reversed-phase HPLC method with the classical post-column OPA derivatization and ion-exchange HPLC procedure. A comparison of UV and fluorescent detection of the amino acid oligomers is also presented. The conclusion reached is that the pre-column OPA derivatization, reversed-phase HPLC and UV detection produces enhanced separation, improved sensitivity and faster analysis than post-column OPA derivatization, ion-exchange HPLC and fluorescence detection.

Amino Acids↗
PubMed1987

Cutaneous leiomyosarcoma: case reports and review of the literature.

Two patients with leiomyosarcomas are described, both men with lesions located in the upper trunk. Both lesions were present for more than 10 years. The diagnosis was established after excisional biopsy. The diagnostic criteria are a tumor size greater than 2.5 cm in diameter; a mitotic rate of 1 or more per 5 high-power fields in cellular areas; and electron microscopic verification of smooth muscle cells. The literature is reviewed and the clinical presentation of the 2 patients is discussed. Wide excision is the treatment of choice after histological diagnosis.

Humans↗
PubMed1987

Benign neoplasms of the oral cavity.

A wide variety of benign tumors present in the oral cavity. These tumors are for the most part rare and are classified by the tissue of origin. Although benign oral cavity tumors are not life-threatening, they can result in extensive loss of soft tissue and/or bone. Furthermore, many patients are subject to the threat of recurrence, multiple surgical procedures, and the possibility of malignant degeneration. Because many tumors vary little clinically, an adequate biopsy specimen must be obtained for diagnosis. Radiographs are, in general, nondiagnostic. Collaboration with an experienced pathologist is necessary to determine the tumor's probable clinical behavior. Therapy, which is dictated by tumor type, is almost always surgical.

Adolescent↗
PubMed1987

Preliminary studies on a more effective phototoxic agent than hematoporphyrin.

Phototoxicity of benzoporphyrin derivative (BPD) has been tested in vitro and compared with that of hematoporphyrin (HP). After 1-hour activation with visible light, BPD was 10 times more cytotoxic than HP toward human adherent cell lines: A549 lung cancer, Calu-1 lung carcinoma, and CCD-19Lu normal lung, killing 100% of cells at the concentration of 70 ng/ml. Under the same conditions, BPD was 10-70 times more cytotoxic than HP toward nonadherent cells and cell lines. Tested were human leukemia cell lines HL60, K562, and KG1, normal human lymphocytes, and mouse mastocytoma cell line P815. The concentrations required to kill 100% of cells varied between 10 and 500 ng BPD/ml and between 0.2 and 10 micrograms HP/ml. The difference between the nonadherent cell lines in respect to their sensitivity to phototoxicity of both BPD and HP seemed to be related to the cell sizes, with the smallest cells being the most vulnerable. The most attractive characteristic of BPD in addition to its powerful phototoxicity is its maximum absorption around 700 nm, which is in the range of wavelengths penetrating tissues the best. This characteristic alone could make BPD a drug of choice in cancer photodynamic therapy when the safety of its use is ensured. Preliminary tests in vivo have shown that DBA/2J mice can tolerate a single ip injection of 20-60 micrograms BPD as well as the same dose of HP. The biodistribution and toxicity studies of BPD are under way in our laboratory.

Animals↗
PubMed1986

Effect of marginal zinc deficiency on the lymphatic absorption of [14C]cholesterol.

The effect of zinc deficiency on intestinal absorption of cholesterol was investigated in adult male rats fed 3.6 ppm of dietary zinc (ZD) and compared with pair-fed (PF) and ad-libitum (CT) controls fed 30.6 ppm of zinc for 10 to 12 wk. The intestinal absorption of cholesterol was measured by collecting the mesenteric lymph at hourly intervals for 8 h after infusing a dose of [14C]cholesterol in a lipid emulsion through an indwelling duodenal catheter. Data on the hourly lymphatic output of [14C]cholesterol showed that the absorption of [14C]cholesterol plateaued at 4 h postdosing in all groups. The rate of the appearance of [14C]cholesterol in the mesenteric lymph significantly decreased in ZD rats at 5 h and thereafter. The cumulative absorption of [14C]cholesterol by ZD rats for the 8-h period was 4.4 +/- 1.0% of the dose, compared with 11.8 +/- 1.1% by PF and 10.7 +/- 1.4% by CT rats. There were no differences in percent distribution of esterified [14C]cholesterol among the three groups. Also, no significant change in mucosal cholesterol esterase activity was observed due to zinc deficiency. The present data and previous findings taken together suggest that the primary mechanism responsible for the impaired absorption of cholesterol may be associated with defective formation of chylomicrons in the intestinal mucosa.

Animals↗
PubMed1985

Warfarin versus dipyridamole-aspirin and pentoxifylline-aspirin for the prevention of prosthetic heart valve thromboembolism: a prospective randomized clinical trial.

In a prospective, randomized, parallel study, two regimens of platelet-suppressant therapy (PST)--dipyridamole-aspirin and pentoxifylline-aspirin--were compared with standard oral anticoagulation with warfarin in the prevention of prosthetic heart valve thromboembolism. In the entire group of 254 patients followed for 395.6 patient-years, the thromboembolic rate was significantly less in the warfarin group (warfarin vs dipyridamole-aspirin, p less than .005; warfarin vs pentoxifylline-aspirin, p less than .05). Subgroup analysis disclosed that, in patients with isolated mitral valve replacement, warfarin was superior to both of the PSTs with respect to the prevention of thromboembolism (warfarin vs dipyridamole-aspirin, p = .005; warfarin vs pentoxifylline-aspirin, p less than .05). Furthermore, a significant number of our patients could not tolerate the antiplatelet agents. However, in the rare situation in which repeated significant bleeding occurs despite careful adjustment of the dosage of warfarin, PST may be an acceptable alternate method of thromboembolism prophylaxis.

Adult↗
PubMed1984

Transcutaneous bilirubin monitoring of newborns.

Using skin jaundice measurements as an index of infant bilirubin status is subject to a number of uncertainties as described by many investigators. They are illustrated by the experience with a commercial device described here. In view of the widespread need for a quantitative measurement that can replace the visual inspections and subjective evaluations of jaundice being routinely used in clinical settings, such jaundice meters are likely to gain increasing acceptance. We expect future research to include more studies on: (1) reflectance spectra or multiple wavelength measurements for SBI; (2) quality control needed for SBI determinations; (3) the relative significance of physiological factors that influence tissue bilirubin deposits; and (4) the comparative significance of blood versus tissue bilirubin concentrations as true indicators of potential nervous tissue damage.

Bilirubin↗